This application is a continuation-in-part of U.S. patent application Ser. No. 14/661,262, filed Mar. 18, 2015, incorporated by reference herein.
The present invention relates to intraocular lenses implanted into the eye for the correction of vision. When a lens is implanted in an eye that contains a natural crystalline lens, the implanted lens is a phakic lens. A phakic lens may be implanted into the anterior chamber, the area behind the cornea and in front of the iris, or into the posterior chamber that is behind the iris. A posterior chamber phakic refractive lens (PRL) is surgically implanted behind the iris and in front of the human natural crystalline lens for correcting ametropia or refractive errors, such as myopia and hyperopia. Implantation of a phakic refractive lens is the only reversible surgical procedure for correcting severe refractive errors in myopic and hyperopic patients. A number of possible complications have slowed the acceptance of this procedure. They are (1) intraocular pressure (TOP) elevation; (2) cataract induction; and (3) iris pigment dispersion. These complications have been linked to lens designs that are permanently fixed in the eye through attachment to anatomical structures such as the ciliary sulcus and iris.
A floating phakic refractive lens has been designed which preserves eye dynamics and greatly reduces the risk of these complications, especially compared to other phakic refractive lens designs. The floating design allows aqueous flow in the eye to reduce or eliminate the risk of intraocular pressure rise and reduces the chance of contact of the refractive lens with the natural crystalline lens that could induce a cataract or forced connection to the iris that causes iris pigment dispersion. A floating lens design has solved these serious problems by its ability to move with the dynamic changes in the eye, such as accommodation, but this freedom of movement can lead to decentration away from the optical center of the eye within the iris opening (pupil). Decentration can be associated with a rare but potentially serious complication, movement of the lens past the zonules and into the vitreous cavity behind the natural crystalline lens. The zonules are fibers connecting the ciliary process of the eye to the natural crystalline lens. In some people, especially those with very high degree of myopia or hyperopia, the zonules may become weakened and/or detached. If one side of a decentered floating phakic refractive lens, the tip of the haptic member, comes to rest on the zonules, loss of zonule integrity could allow the resting lens to slip through the gap. An additional surgical manipulation would then be required to retrieve the phakic refractive lens.
An improved method for centering the phakic refractive lens that preserves the benefits of that design and does not depend on problematic permanent fixation is needed.
There are a number of patents describing the posterior chamber phakic refractive lens concept and specific lens designs. U.S. Pat. No. 4,585,456, Blackmore, issued Apr. 29, 1986, discloses a phakic intraocular lens composed of flexible materials which is positioned against the natural lens of the eye and is held in place immediately adjacent to the natural lens and the ciliary sulcus. The lens is fixed in place, rather than floating. It assumes that stable centration is achieved by fixing the position of the lens through direct and constant contact with the tissues and structures of the eye. Intraocular pressure elevation and cataract formation are complications from such a lens design. These complications are documented by Fechner, et al, in the Journal of Cataract and Refractive Surgery, March 1996, Volume 22, pages 178-81. Even in a fixed lens that has a length matched to the diameter of the eye, which is difficult to achieve, the lens will eventually contact the natural lens, resulting in a subcapsular cataract. This is because the natural lens grows throughout life and will eventually press against the fixed refractive lens.
Other patents describe different ways of reducing intraocular pressure elevation and avoiding cataract formation by phakic refractive lens designs and their fixation mechanisms. Fedorov, in U.S. Pat. No. 5,480,428, issued Jan. 2, 1996, discloses a novel phakic lens design with an opening through the center of the optic body. This open hole allows aqueous humor to flow through the lens body, from its source in the posterior chamber to the anterior chamber of the eye. The hole is designed to restore aqueous flow and reduce intraocular pressure that builds when the lens body blocks the iris opening. The hole was also found to reduce the optical performance of the lens. Fedorov, in U.S. Pat. No. 5,258,025, issued Nov. 2, 1993, discloses that post-operative inflammation, caused by the supporting element's contact with ocular tissue, is prevented by moving supporting elements to the periphery of the phakic lens. The patent teaches that the Zinn's zonules are strong enough to hold the supporting elements in place without causing inflammation. Feingold, in U.S. Pat. No. 5,913,898, issued on Jun. 22, 1999, discloses an improvement of the Fedorov posterior chamber phakic refractive lens design with the supporting elements placed in the ciliary sulcus; the lens includes a hole in the center of the optic for equalizing pressure in the eye. These fixed designs are wide and span the inner diameter of the posterior chamber, effectively blocking the aqueous flow from the anterior chamber where it should exit the eye. The natural pressure equalizing mechanism has been compromised, effectively creating conditions that could lead to glaucoma. A hole in the lens allows the aqueous flow to be re-established. A number of later patent applications, such as Patel, US Published Application 2003/0204253, published Oct. 30, 2003, and Bogaert, US Published Application 2005/0149184, published Dec. 14, 2004, disclose holes or penetrating channels in the phakic lens body for the purpose of allowing aqueous flow that are said to prevent intraocular pressure increases. These are posterior chamber phakic lens designs that are fixed in place and use a hole in the optic body to reduce intraocular pressure that may lead to glaucoma.
Kawamorita et al, in “Fluid Dynamics Simulation of Aqueous Humor in a Posterior-Chamber Phakic Intraocular Lens with a Central Perforation”, Graefes Arch Clin Exp Ophthalmol (2012), Volume 250: 935-939, discuss a computer model of the flow of aqueous humor through a hole in the center of the optic of a posterior chamber phakic refractive lens. The authors indicate that the hole was created to allow increased aqueous flow between the natural lens and phakic implanted lens and to equalize pressures in the eye. The analysis shows that aqueous humor is channeled through the center hole at a higher rate than the flow around the lens body. The analysis also showed that the flow velocity between the anterior surface of the natural crystalline lens and the posterior surface of the posterior chamber phakic lens is increased relative to the situation with the same phakic lens design without a center hole. In this case, the lens design includes fixation of the haptic members in the ciliary sulcus. In other words, the lens is not a floating design.
The floating phakic refractive lens design is disclosed in Valyunin, et al, U.S. Pat. No. 6,015,435, issued Jan. 18, 2000, and U.S. Pat. No. 6,428,574, issued Aug. 6, 2002. The floating lens design has an annular ring around the optic area, in the case of a lens for the correction of myopia, or a protruding optic, in the case of a lens designed for treatment of hyperopia, that comes in contact with the edge of the iris, the iris thereby applying a centering force to the lens. A haptic member is attached to the optic that is designed to prevent the optic from being grossly decentered away from the pupil. The haptic is designed with a curvature substantially equivalent to the curvature of the natural lens (see FIG. 1 and FIG. 6 of Valyunin). This floating lens design works with the iris to channel aqueous flow around the lens to reduce the risk of intraocular pressure rise and help to maintain a gap between the implant and the natural lens. The floating behavior of the lens is further assured by matching the material properties of the lens to the aqueous medium of the eye, disclosed in U.S. Pat. No. 6,706,066, Zhou et al, issued Mar. 16, 2004. The specific gravity and mass per unit surface area of the phakic lens material are combined with the phakic lens design to cause the lens to float in the eye and allow the eye dynamics to help maintain the position and centration of the phakic refractive lens. Koivula, et al, in Opthalmology (2007), Volume 114, pages 2031-2037, used optical coherence tomography imaging to show that such a lens moves with the natural eye dynamics to allow a normal aqueous humor flow inside the posterior chamber.
Perez-Cambrodi, et. al., in the Journal of Optometry July 2012, Volume 5, pages 121-130, found, in an analysis of a series of patients implanted with floating phakic refractive lens, that there was contact between one of the haptic members and the zonules in some cases. Positional analysis indicated a trend toward nasal decentration. This did not have a significant effect on the performance of the phakic refractive lens, but continued contact of the phakic refractive lens with the zonules could eventually lead to the complication of zonular dehiscence and dislocation of the lens toward the vitreous chamber (the back of the eye near the retina). Adding an additional design feature that could preserve a floating feature could have significant patient benefits while improving centration of the lens would be a significant improvement, further reducing risks associated with an anatomically compatible phakic refractive lens designed to restore emmetropia in myopic or hyperopic human eyes.